Remove coverage env from travis config.
Remove coverage env from travis config.

Signed-off-by: Jannis Leidel <9b7c7d158dc2d8ee5ad777a516c517e4cfb54547@leidel.info>

seenureddy/django-configurations,cato-/django-configurations,blindroot/django-configurations,pombredanne/django-configurations,incuna/django-configurations,jezdez/django-configurations,nangia/django-configurations,jazzband/django-configurations,jazzband/django-configurations,NextHub/django-configurations,gatherhealth/django-configurations